Multi-band identification and ranging

ABSTRACT

A long-range power-efficient multiple-band identification system and method includes, for example, a base-station control module and paired electronic key fob. The base-station control module and paired electronic key fob is arranged to provide a UHF (ultra-high frequency) wake transmitter for transmitting a wakeup signal in a UHF frequency range to the paired electronic key. When in range, the electronic key is awakened by the wakeup signal and in response transmits an acknowledgment reply to the base-station control module. After receiving the acknowledgment, the base-station control module transmits a relatively high power localization signal for determining an electronic key location.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/658,763, filed Jul. 25, 2017 and now issued U.S. Pat No. 10,008,062,which is a continuation of U.S. application Ser. No. 14/452,464, filedAug. 5, 2014 and now issued U.S. Pat. No. 9,747,736, each of which areincorporated herein by reference in its entirety.

BACKGROUND

Conventional wireless access systems provide mechanisms foridentification as well as ranging. The identification and rangingmechanisms provide information used to determine whether to allow accessto secured areas such as in buildings, secured outdoor areas, and/orvehicles. For example, many automobiles are sold having key fobs thatare electronically matched with a particular vehicle and allow a holderof the key fob to gain access to and operate the particular vehicle. Thefunctionality of the key fobs and associated control systems is beingincreased to response to ever-increasing demands for increased securityby individual users and automobile insurance companies, among others.

The key fob is arranged to wirelessly communicate with a base-stationcontrol module that is powered by a battery (which often stores upwardsof 100 amp-hours) of the particular vehicle. In contrast, the key fob isportable and designed to be light weight and to easily fit in the palmof a hand, pocket, or a purse, for example. As the functionality of thekey fob-actuated systems increase, the demand for power by theelectronic circuit designs and applications that provide thefunctionality increase. The increase in power usage can, for example,which can shorten the operating time before having to recharge orreplace batteries in the vehicle and/or key fob.

SUMMARY

The problems noted above can be addressed in a multiple-bandidentification and ranging system and method includes, for example, abase-station control module and paired electronic key fob. Thebase-station control module and paired electronic key fob is arranged toprovide a UHF (ultra-high frequency) wake transmitter for transmitting aUHF wakeup signal to the paired electronic key. When in range, theelectronic key is awakened by the wakeup signal and in responsetransmits an acknowledgment reply to the base-station control module.After receiving the acknowledgment, the base-station control moduletransmits a relatively high power localization signal for determining anelectronic key location.

This Summary is submitted with the understanding that it is not be usedto interpret or limit the scope or meaning of the claims. Further, theSummary is not intended to identify key features or essential featuresof the claimed subject matter, nor is it intended to be used as an aidin determining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an illustrative electronic device in accordance withexample embodiments of the disclosure.

FIG. 2 is a block diagram illustrating a conventional base-stationcontrol module (BCM).

FIG. 3 is a block diagram illustrating a conventional electronic key.

FIG. 4 is a system diagram illustrating communications of a conventionalradio identification and ranging system.

FIG. 5 is a block diagram illustrating a multiple-band base-stationcontrol module of a host vehicle in accordance with example embodimentsof the disclosure.

FIG. 6 is a block diagram illustrating a multiple-band electronic key inaccordance with example embodiments of the disclosure.

FIG. 7 is a system diagram illustrating communications of amultiple-band identification and ranging system in accordance withexample embodiments of the disclosure.

FIG. 8 is a system diagram illustrating relative ranges of amultiple-band identification and ranging system in accordance withexample embodiments of the disclosure.

DETAILED DESCRIPTION

The following discussion is directed to various embodiments of theinvention. Although one or more of these embodiments may be preferred,the embodiments disclosed should not be interpreted, or otherwise used,as limiting the scope of the disclosure, including the claims. Inaddition, one skilled in the art will understand that the followingdescription has broad application, and the discussion of any embodimentis meant only to be example of that embodiment, and not intended tointimate that the scope of the disclosure, including the claims, islimited to that embodiment.

Certain terms are used throughout the following description—andclaims—to refer to particular system components. As one skilled in theart will appreciate, various names may be used to refer to a componentor system. Accordingly, distinctions are not necessarily made hereinbetween components that differ in name but not function. Further, asystem can be a sub-system of yet another system. In the followingdiscussion and in the claims, the terms “including” and “comprising” areused in an open-ended fashion, and accordingly are to be interpreted tomean “including, but not limited to . . . .” Also, the terms “coupledto” or “couples with” (and the like) are intended to describe either anindirect or direct electrical connection. Thus, if a first devicecouples to a second device, that connection can be made through a directelectrical connection, or through an indirect electrical connection viaother devices and connections. The term “portion” can mean an entireportion or a portion that is less than the entire portion. The term“calibration” can include the meaning of the word “test.” The term“input” can mean either a source or a drain (or even a control inputsuch as a gate where context indicates) of a PMOS (positive-type metaloxide semiconductor) or NMOS (negative-type metal oxide semiconductor)transistor. The term “pulse” can mean a portion of waveforms such asperiodic waveforms. The term “transceiver” includes the meaning oftransmitter and receiver, where the transmitter and receiver areindependently operable of each other (e.g., both can be on, either canbe on, and both can be off during operation of the system that includesthe transceiver).

FIG. 1 shows an illustrative computing system 100 in accordance withpreferred embodiments of the disclosure. For example, the computingsystem 100 is, or is incorporated into, an electronic system 129, suchas a computer, electronics control “box” or display, communicationsequipment (including transmitters), or any other type of electronicsystem arranged to generate radio-frequency signals.

In some embodiments, the computing system 100 comprises a megacell or asystem-on-chip (SoC) which includes control logic such as a CPU 112(Central Processing Unit), a storage 114 (e.g., random access memory(RAM)) and a power supply 110. The CPU 112 can be, for example, aCISC-type (Complex Instruction Set Computer) CPU, RISC-type CPU (ReducedInstruction Set Computer), MCU-type (Microcontroller Unit), or a digitalsignal processor (DSP). The storage 114 (which can be memory such ason-processor cache, off-processor cache, RAM, flash memory, or diskstorage) stores one or more software applications 130 (e.g., embeddedapplications) that, when executed by the CPU 112, perform any suitablefunction associated with the computing system 100.

The CPU 112 comprises memory and logic that store information frequentlyaccessed from the storage 114. The computing system 100 is oftencontrolled by a user using a UI (user interface) 116, which providesoutput to and receives input from the user during the execution thesoftware application 130. The output is provided using the display 118,indicator lights, a speaker, vibrations, and the like. The input isreceived using audio and/or video inputs (using, for example, voice orimage recognition), and electrical and/or mechanical devices such askeypads, switches, proximity detectors, gyros, accelerometers, and thelike. The CPU 112 is coupled to I/O (Input-Output) port 128, whichprovides an interface that is configured to receive input from (and/orprovide output to) networked devices 131. The networked devices 131 caninclude any device (including key fobs or base-station control modulesthat are electronically paired with the computing system 100) capable ofpoint-to-point and/or networked communications with the computing system100. The computing system 100 can also be coupled to peripherals and/orcomputing devices, including tangible, non-transitory media (such asflash memory) and/or cabled or wireless media. These and other input andoutput devices are selectively coupled to the computing system 100 byexternal devices using wireless or cabled connections. The storage 114can be accessed by, for example, by the networked devices 131.

The CPU 112 is coupled to I/O (Input-Output) port 128, which provides aninterface that is configured to receive input from (and/or provideoutput to) peripherals and/or computing devices 131, including tangible(e.g., “non-transitory”) media (such as flash memory) and/or cabled orwireless media (such as a Joint Test Action Group (JTAG) interface).These and other input and output devices are selectively coupled to thecomputing system 100 by external devices using wireless or cabledconnections. The CPU 112, storage 114, and power supply 110 can becoupled to an external power supply (not shown) or coupled to a localpower source (such as a battery, solar cell, alternator, inductivefield, fuel cell, capacitor, and the like).

The computing system 100 includes vehicle radio identification andranging modules 138. The computing system 100 includes a long rangebase-station control module (LRBCM) 140 (such as long-range base-stationcontrol module 502 discussed below discussed below with reference toFIG. 5) and long-range key (LRKEY) 142 (such as key fob 600 discussedbelow with reference to FIG. 6). The LRBCM 138 is adapted formultiple-band (UHF and LF) identification and ranging.

The disclosed multiple-band identification and ranging system addresses,for example, issues of conserving power and accurately localizing aportable electronic key fob. The multiple-band identification andranging system includes a very low (e.g., not noticeable by a user)latency ultra-low power UHF receiver integrated with an on-demand,precise low frequency (LF) radio ranging system. The combination of lowlatency, low power, long-range, and other such requirements tends tolimit the operating range of communications over the LF frequency range(e.g., channel) due to the key fob sensitivity and the maximum transmitpower on the base-station side. The latency and sensitivity of the keyfob is limited by the capacity of the small battery in the key fob,while transmit power of the polling vehicle side is limited by thecapacity of the vehicle battery. Conventional systems are discussedbelow with reference to FIG. 2, FIG. 3, and FIG. 4.

FIG. 2 is a block diagram illustrating a conventional base-stationcontrol module (BCM). Generally described, a host vehicle 200 includes abase-station control module 202, an embedded processor 210, anultra-high frequency (UHF) receiver 220, a low frequency (LF)transmitter 230, interfaces 240, power supply 250, and a car battery260.

The embedded processor 210 is coupled to the UHF receiver 220, the LFtransmitter 230, the system interface 240, and the power supply 250. Theembedded processor 210 is a processor such as CPU 112 and is arranged toexecute instructions for initializing and handling tasks associated withthe functions of the various components of the base station controlmodule 202. The embedded processor 210 includes serial-to-parallelinterfaces (SPI) 212 and 214.

The SPI 212 is coupled to the UHF receiver 220 and is arranged forcoupling communications between the UHF receiver 220 and the embeddedprocessor 210. Such communications include, for example, configurationand status commands sent by the embedded processor 210 to the UHFreceiver 220 and receiving information received by the UHF receiver 220via antenna 222.

The SPI 214 is coupled to the LF transmitter 230 and is arranged forcoupling communications between the LF transmitter 230 and the embeddedprocessor 210. Such communications include, for example, configurationand status commands sent by the embedded processor 210 to the LFtransmitter 230 as well as sending control and information to the LFtransmitter 230 for transmission via one or more stick antennas such asstick antennas 232, 234, 236, and 238.

The base-station control module 202 is arranged with a system interface240 for sending and receiving information across one or more networks ofthe host vehicle 200. For example, the base-station control module 202is arranged to wirelessly query the electronic key (e.g., usingencrypted communications) to authenticate whether the key fob has been“paired” (e.g., having been provisioned with one or more encryption keysfor establishing a secure communication link) with the base-stationcontrol module 202. After authentication (e.g., identification) of thekey fob, the system interface 240 sends an indication of the positivestatus of the authentication to one or more components of the hostvehicle 200 across respective networks of the host vehicle 200. The oneor more components of the host vehicle 200, for example, respond to theindication of the positive status of the authentication by allowingaccess for controlling the one or more components of the host vehicle200.

The power supply 250 is arranged to receive power from the car battery260 that is used to power the host vehicle 200. Such power is typicallyunregulated and has a normal voltage operating range of 7 to 16 volts(nominally 12 volts). The power supply 250 is typically a low dropout(LDO) power supply is arranged for supplying power to active componentsof the base-station control module. The output voltage of the powersupply 250 is regulated at 5 volts over the normal operating voltagerange of the car battery 260.

FIG. 3 is a block diagram illustrating a conventional electronic key.Generally described, key fob 300 is an electronic key that includes apower source (such as coin cell 302), buttons 304, indicator 306, apassive entry device 310, UHF transmitter 320, and three-dimensional(3D) LF antenna 330. Cell 302 is arranged for providing power to activecomponents of electronic UHF of the key fob 300. Buttons 304 arearranged for providing user input so that a user can select a commandfor transmitting to a paired base-station control module (such asbase-station control module 202). Selectable commands include “lock,”“unlock,” “panic,” and the like. Indicator 306 is arranged to provide anindication of functioning of the key fob 300.

The passive entry device 310 includes a 16 bit microcontroller 340,Advanced Encryption Standard (AES) hardware (HW) encryption module 342,secure EEPROM (electrically erasable programmable nonvolatile memory)344, three-dimensional wake receiver 346, and three-dimensionalimmobilizer 348. The passive entry device 310 is arranged forcommunicating with base-station control module 202 via the UHFtransmitter 320 (and UHF transmitter antenna 322) and thethree-dimensional LF antenna 330. Such communications are describedbelow with respect to FIG. 4.

FIG. 4 is a system diagram illustrating communications of a conventionalradio identification and ranging system. Generally described, system 400includes a base-station control module 202 that has been paired with akey fob 300. In an example scenario, key fob 300 is in a sleep mode,which reduces power consumption of the (e.g., battery-operated) key fob300.

When a user of the key fob 300 approaches within around 2-4 meters of anantenna of a base-station control module 202 that is located in a hostvehicle 200, the three-dimensional wake receiver 346 of the key fob 300detects an LF wake signal 402. (The LF wake signal 402 is transmitted bythe LF transmitter 230 for example in response to door handle activityor on a repeated basis every few hundreds of milliseconds.) When thethree-dimensional wake receiver 346 detects an LF wake signal 402, thethree-dimensional wake receiver 346 commands the key fob 300 to exit thesleep mode and enter an active mode (which increases power consumptionof the key fob 300).

When the key fob 300 enters the active mode, the key fob 300 transmits aUHF signal 404 to, for example, initiate authentication procedures anddetermine a relative position of the key fob 300 to the host vehicle200. The UHF signal 404 typically is transmitted over a range of greaterthan 30 meters in response to a user pressing a button 304. Thetransmission of the UHF signal 404 at a range of greater than 30 metersconsumes substantially more power than transmission of a short rangesignal, such as the LF wake signal 402, which typically has a range ofaround 2-4 meters.

The system 400 includes functionality for vehicle identification as wellas for relative position ranging of the host vehicle 200 and the key fob300. Such relative positioning is used to help avoid vehicle theft aswell as accidental starting of the vehicle from the outside, forexample. The combination of these two functions often result in alimited operating range over the low frequency (LF) channel because ofthe (e.g., lower) key fob 300 sensitivity and the (e.g., limited)maximum transmit power of the base-station control module 202 from thehost vehicle 200. For example, the key fob 300 sensitivity is limited bythe relatively small capacity (e.g., around 230 milliamp-hours) of thesmall battery in the key fob 300, while the transmit power of thecontinuously polling from the host vehicle 200 is limited by thecapacity of the car battery 260. In contrast, a long-range portableradio identification and ranging system and method is disclosed hereinthat includes a relatively low latency ultra-low power UHF transceiverand an on-demand precision LF radio ranging system.

FIG. 5 is a block diagram illustrating a multiple-band base-stationcontrol module of a host vehicle in accordance with example embodimentsof the disclosure. Generally described, of a host vehicle 500 includes along-range base-station control module 502. The long-range base-stationcontrol module 502 includes an embedded processor 510, an ultra-highfrequency (UHF) transceiver 520, a low frequency (LF) transceiver 530,interfaces 540, power supply 550, and a transportable power source suchas car battery 560.

The ultra-high frequency (UHF) transceiver 520 includes a highperformance UHF transceiver 526. The high performance UHF transceiver526 is arranged to generate and transmit a wakeup signal using one ormore selected frequencies in a frequency range of 300 MHz through 2.4GHz (UHF). The high performance UHF transceiver 526 is arranged totransmit and receive normal power communications between the hostvehicle 500 and the paired key fob (e.g., the high performance UHFtransceiver 526 can be powered up from a sleep mode and activated afterthe key fob 600 has been awakened by the transmitted wakeup signal,discussed below). The disclosed long-range base-station control module502 saves power because, for example, the lower-power-consuming UHFtransceiver 526 is used for transmitting the wakeup signal (in contrastwith conventional systems which normally continuously broadcast thewakeup signal using the higher power-consuming LF transmissions).

The UHF transceiver 526 typically consumes a supply current in the rangeof 10 mA to 40 mA as compared with the LF transceiver 530, which insteadconsumes a supply current in the range of 1 A to 4 A (e.g., which issupplied from a battery that often contains less than 100 amp-hours ofcharge). Accordingly, the disclosed long-range base-station controlmodule 502 in an embodiment can have a reduced current draw by a factorof 100 over conventional solutions. Also, the far-field (e.g., E-field)damping of UHF frequencies is 20 dB/decade, which allows a highercommunication ranges than ranges achieved using LF frequencies (whichhas near-field, e.g., H-field, damping of 60 dB/decade). Because thestrong decay of the LF near-field allows for much superior rangeresolution (e.g., over UHF-based localization), the LF transceiver 530is normally used for localization of the key fob 600.

The UHF transceiver 526 provides a low-power, long-range solution forpolling the key fob 600 by sending a short, periodic UHF signal from thehost vehicle 500 to query the key fob 600. The key fob is arranged toreceive the query within a range of more than 10 meters. When the keyfob 600 is in range, the key fob 600 receives the query and in responsesends an appropriate acknowledgement response. When the acknowledgementresponse is correct, the host vehicle 500 can, for example, execute anintended function such as “welcome illumination” or other comfortfunctions. At this point, the location of the key fob 600 has not yetbeen precisely localized, for example, because of the UHF frequencydamping characteristics. To more accurately localize the key fob 600within a closely defined range, the key fob 600 is operable to perform aLF received signal strength indicator (RSSI) measurement and send thedetermined RSSI information to the long-range base-station controlmodule 502.

The embedded processor 510 is coupled to the UHF transceiver 520, the LFtransceiver 530, the system interface 540, and the power supply 550. Theembedded processor 510 is a processor such as CPU 112 and is arranged toexecute instructions for initializing and handling tasks associated withthe functions of the various components of the long-range base stationcontrol module 502 (as described below). The embedded processor 510includes serial-to-parallel interfaces (SPI) 512 and 514.

The SPI 512 is coupled to the UHF transceiver 520 and is arranged forcoupling communications between the UHF transceiver 520 and the embeddedprocessor 510. Such communications include, for example, configurationand status commands sent by the embedded processor 510 to the UHFtransceiver 520 and sending information to and receiving informationfrom the UHF transceiver 520. The UHF transceiver 520 is arranged fortransmitting and receiving via antenna 522.

The SPI 514 is coupled to the LF transceiver 530 and is arranged forcoupling communications between the LF transceiver 530 and the embeddedprocessor 510. Such communications include, for example, configurationand status commands sent by the embedded processor 510 to the LFtransceiver 530 as well as sending information to and receivinginformation from the LF transceiver 530. The LF transceiver 530 istypically activated after wakeup and query functions have been executed.

The LF transceiver 530 generates a low frequency (LF) signal (18-150kHz), which can be used for precise localization of the key fob 600. TheLF transceiver 530 is arranged for transmitting and receiving via one ormore stick antennas such as stick antennas 532, 534, 536, and 538. Aplurality of stick antennas can be used to enhance the accuracy (e.g.,over signal-strength-only calculations) by using triangulation methods(such as time-of-arrival comparisons) that evaluate signals receivedfrom the plurality of stick antennas that are located in variouslocations around the vehicle. Accordingly, the location of the key fob600 can be determined (e.g., such as whether the key fob is inside thehost vehicle 500, on the driver's side, on the passenger's side, and thelike) so that commands (such as starting the car) can be selectivelyenabled in accordance with the determined location of the key fob 600.

The long-range base-station control module 502 is arranged with a systeminterface 540 for sending and receiving information across one or morenetworks of the host vehicle 500. For example, the long-rangebase-station control module 502 is operable to control access to variousfunctions of the host vehicle in response to communications with the keyfob 600.

The power supply 550 is arranged to receive power from a transportablepower source such as the car battery 560 that is used to power the hostvehicle 500. The transportable power source is a power source (such as acar battery) and is arranged for providing power to active components ofthe long-range base-station control module 502. The transportable powersource can be battery, solar cell, alternator, inductive field, fuelcell, capacitor, and the like such that the host vehicle 500 is capableof normal operation without being physically tethered (e.g., via a powercord) to utility-supplied power, for example. The transportable powersupply has physical format (such as dimensions and weight) that issuited for being transported in an operational vehicle (e.g., that cancarry persons using the key fob 600).

The transportable power supply is for providing power that is typicallyunregulated and has a normal voltage operating range of 7 to 16 volts(nominally 12 volts). The power supply 550 is typically a low dropout(LDO) power supply is arranged for supplying power to active componentsof the base-station control module. The output voltage of the powersupply 550 is regulated at 5 volts over the normal operating voltagerange of the car battery 560.

FIG. 6 is a block diagram illustrating a multiple-band electronic key inaccordance with example embodiments of the disclosure. Generallydescribed, key fob 600 is an electronic key that includes a portablepower source (such as coin cell 602), buttons 604, indicator 606, apassive entry device 610, UHF antenna 622, and a three-dimensional (3D)LF antenna 630 (which is arranged for communicating with each of thestick antennas 532, 534, 536, and 538 of LF transceiver 530 beingpositioned and oriented to allow for precise localization of the key fob600).

The portable power source is a power source (such as coin cell 602) andis arranged for providing power to active components of electronic UHFof the key fob 600. The portable power source can be battery, solarcell, alternator, inductive field, fuel cell, capacitor, and the likesuch that the key fob 600 is capable of normal operation without beingphysically tethered (e.g., via a power cord) to utility-supplied power,for example. The portable power supply has physical format (such asdimensions and weight) that is suited for being carried by a normalperson using the key fob 600.

Buttons 604 are arranged for providing user input so that a user canselect a command for transmitting to a paired base-station controlmodule (such as long-range base-station control module 502). Selectablecommands include “lock,” “unlock,” “panic,” and the like. Indicator 606is arranged to provide an indication of functioning of the key fob 600.

The passive entry device 610 includes a UHF wake receiver 624, a highperformance UHF transceiver 626, a 32-bit microcontroller 640, a securecryptography (crypto) peripheral 642, a secure memory such as FRAM(ferroelectric RAM) 644, a three-dimensional wake receiver 646, and athree-dimensional immobilizer 648. The passive entry device 610 isarranged for communicating with the long-range base-station controlmodule 502 via the UHF transceiver 626 (and UHF antenna 622) and thethree-dimensional LF antenna 630.

The 32-bit microcontroller 640 is arranged to control and coordinate thevarious components of the passive entry device 610 and to provideprocessing support to the various components as needed. The securecryptographic peripheral 642 is arranged to execute and/or facilitateexecuting cryptographic instructions used for authentication and securecommunications. The secure FRAM 644 is an example non-volatile memoryfor storing data and computer executable instructions used by the 32-bitmicrocontroller 640 and the secure cryptographic peripheral 642.

The passive entry device 610 includes an LF backup channel for passiveentry functions in situations where UHF noise is sufficiently high toblock reception of a UHF wakeup signal. The three-dimensional wakereceiver 646 is responsive to an LF wakeup signal, should an LF wakeupsignal be optionally broadcast by the long-range base-station controlmodule 502. The LF wakeup signal can optionally be transmitted(periodically or intermittently) in response to a measurement of anamount of UHF noise that exceeds a threshold. Similarly the LF wakeupsignal can optionally be transmitted periodically, such as once persecond, which typically does not result in a noticeable delay by a userof the key fob 600. The LF wakeup signal can be transmitted in aninterleaved manner so that one or more UHF wakeup signals are sent inbetween the transmission of two (e.g., otherwise consecutive or adjacentin time) LF wakeup signals.

The three-dimensional immobilizer 648 is operable to provide backupaccess to the host vehicle 500 in case, for example, of a substantiallydischarged key fob battery 602. When the key fob 600 is in closeproximity (such as less than around 10 cm) of an antenna (such as one ofthe stick antennas 532, 534, 536, and 538), the key fob receivesoperational power from an LF field generated by the antenna (e.g.,instead of the discharged the battery). The three-dimensionalimmobilizer 648 allows start of the host vehicle 500 engine aftersuccessful authentication of the key fob 600 (which is then beingpowered by host vehicle 500-supplied power).

The wake receiver 624 is responsive to an UHF wakeup signal that istransmitted using one or more selected frequencies in a frequency rangeof 300 MHz through 2.4 GHz (UHF). The wake receiver 624 is arranged towake up one or more active components of the passive entry device 602,including the high performance UHF transceiver 626. The wake receiver624 operates (e.g., in sleep mode) by scanning the receiver input forthe wakeup pattern (which is normally provisioned as stored data whenthe key fob 600 is paired with the long-range base-station controlmodule 502). In an example embodiment, the wake receiver 624 consumesless than 1 μA (micro-Ampères) of power when operating at 128 bits persecond with 242 ms (millisecond) latency and consumes less than 5 μA ofpower when operating at 1024 bits per second with 30.5 ms latency.

The high performance UHF transceiver 526 is arranged to transmit andreceive UHF communications between the host vehicle 500 and the pairedkey fob (such as key fob 600). Such communications are described belowwith respect to FIG. 7.

FIG. 7 is a system diagram illustrating communications of amultiple-band identification and ranging system in accordance withexample embodiments of the disclosure. Generally described, system 700includes a long-range base-station control module 502 that has beenpaired with a key fob 600.

As described above, the paired key fob 600 includes transmitters andreceivers suitable for communicating with the long-range base-stationcontrol module 502. The paired key fob 600 is typically provisioned withencryption keys and protocols that are paired to the long-rangebase-station control module 502. The paired key fob 600 (including anyduplicates, spares, or replacement key fobs) is uniquely provisioned(e.g., by a vehicle manufacturer or dealer) to provide exclusive and/orsecure communications to the long-range base-station control module 502.Accordingly, the paired key fob 600 can be uniquely authenticated by thelong-range base-station module 502.

In an example scenario as illustrated in FIG. 7, key fob 600 isinitially in a sleep mode, during which the power consumption of the(e.g., battery-operated) key fob 600 is greatly reduced (e.g., toconserve battery charge). The key fob 600 is typically carried in apurse, pocket, or hand of a user, and is arranged to be activated byproximity to the long-range base-station control module 502 despite avariety of possible (e.g., physical) orientations of the key fob 600.Accordingly, the key fob 600 functions as a passive entry device, whichtypically does not require intentional user input to trigger at leastsome functions of the key fob 600 (e.g., including a wakeup function ofkey fob 600).

When a user of the key fob 600 approaches a location within around 10 ormore meters of an antenna of a long-range base-station control module502 that is located in a host vehicle 500, the wake receiver 624 of thekey fob 600 detects a UHF wakeup signal 702 that is transmitted by theUHF high performance UHF transceiver 526 of the long-range base-stationcontrol module 502. The UHF wake signal 702 is normally transmitted bythe UHF wake transmitter 530 on a continuous or repeated (e.g., toreduce power consumption of the host vehicle 500 car battery) basis toreduce latency times in waking up the key fob 600. For example, the wakesignal 702 can be transmitted once every second such that user of thekey fob 600 does not encounter any noticeable delay (e.g., due tolatency encountered when electronically unlocking the host vehicle 500)when entering the host vehicle 500. The UHF wake transmitter is arrangedto stop transmitting the UHF wake signal 702 in response to anindication from key fob 600 is in an active mode (e.g., has been wokenup by the UHF wake signal 702).

The wake receiver 624 of the key fob 600 is arranged to detect the UHFwakeup signal 702, at a range of over 10 meters. The wake receiver 624is arranged to receive the wakeup signal 702 despite being oriented inany of a number of directions (e.g., while being in a purse, pocket, orhand). When the wake receiver 624 detects the UHF wakeup signal 702, thewake receiver 624 directs one or more components of the key fob 600 toexit a low power mode (e.g., a sleep mode) and enter an active mode(which increases power consumption of the key fob 600) where activecomponents of the passive entry device 610 are actively powered.

When the key fob 600 enters the active mode (e.g., where the highperformance UHF transceiver 626 is powered up), the key fob 600transmits a UHF signal 704, for example, to initiate authenticationprocedures for authenticating the key fob 600 to the long-rangebase-station control module 502. The UHF signal 704 is transmitted usinga power that, at least, is sufficient to cover the current distance ofthe key fob 600 to the host vehicle 500 (which, per the range of thewakeup signal 702, can be up to around 10 meters or more). When thecredentials supplied by the key fob 600 in the UHF signal 704 arevalidated by the long-range base-station control module 502, the hostvehicle 500 can, for example, execute one or more limited functions suchas a “welcome illumination” or other comfort functions. Because, at thispoint in time, the key fob 600 has not been precisely localized, thefunctions available for execution are can be limited (e.g., such thatstarting the host vehicle is prohibited when the location of the key fob600 has not been precisely localized).

To precisely localize the key fob 600, the long-range base-stationcontrol module 502 is arranged to use an LF channel to determine a moreaccurate location of the key fob 600 with respect to the host vehicle500. The LF transceiver 530 is coupled to the each of the stick antennas532, 534, 536, and 538. The LF transceiver 530 is arranged to perform alocalization routine (such as an RSSI routine) to determine a relativelocation of the key fob 600 by transmitting one or more signals such asLF signal 706 via each of the stick antennas used in the localizationroutine.

The LF signal 706 is transmitted using a power level that, at least, issufficient to cover the distance of the host vehicle 500 to the key fob600 when the key fob is in a close or intermediate range (such as withinaround 4 through 6 meters). The LF signal 706 can be transmitted using ahigher power level to achieve a range (such as around 6 through 10 ormore meters) and/or by using a higher-sensitivity three-dimensional wakereceiver 646 for RSSI measurement, which is substantially close to therange of the UHF wakeup signal 702. Despite the increase in powerrequired using the LF channel, increased resolution in the localizationdetermination is achieved because of the avoidance of UHF damping thatoccurs in greater distances (such as distances greater than 4 meters)when using a UHF channel for localization. Accordingly, a location ofthe key fob 600 relative to each participating stick antenna can bedetermined, and a precise location of the key fob 600 is determined inresponse to evaluating the relative locations of the key fob 600 to therespective stick antenna.

In response to receiving one or more signals such as LF signal 706, thekey fob 600 generates one or more localization reply signals, such assignal 708. Signal 708 is typically transmitted as a UHF signal via highperformance UHF transceiver 626, although the LF channel can be used(e.g., on-demand in situations where substantial amounts of UHF noiseare detected). The signal 708 can be transmitted using high power suchthat the signal 708 can be received by the long-range base-stationmodule 502 at distances of more than around 100 meters (and, forexample, to be intelligible in the presence of UHF noise). Thelocalization reply signals received by the long-range base-stationcontrol module 502 can be used to determine a precise, relative locationof the key fob 600 to the host vehicle 500 (in accordance with thearrangement of the stick antennas on the host vehicle that participatein the localization routine) as described above.

FIG. 8 is a system diagram illustrating relative ranges of amultiple-band identification and ranging system in accordance withexample embodiments of the disclosure. Generally described, system 800includes a secure area such the interior 812 of host vehicle 810. Thehost vehicle 810 includes a long-range base-station control module 502(as illustrated in FIG. 5). Host vehicle 810 is a vehicle such as hostvehicle 500. In various embodiments, secure area can be a vehicle,building, room, outdoor area, device, and the like for which physicaland/or functional access restrictions are desired.

The long-range base-station control module 502 is coupled to the stickantennas 532, 534, 536, and 538, which are arranged in various positions(not shown) of the host vehicle 810 to optimize the performance of thelocalization routines. The stick antennas 532, 534, 536, and 538 arearranged such that the localization routines are able to determine therelative location of the key fob 600 (e.g., the polar or rectangularcoordinates of key fob 600 with respect to a reference point that isassociated with the host vehicle 500). The stick antennas 532, 534, 536,and 538 are also arranged such that the localization routines are ableto determine whether the key fob 600 is in the interior 812 of the hostvehicle 810.

Various transmission ranges are illustrated with respect to the hostvehicle 810. The actual limits of the various transmission ranges varyin response to operational conditions such as atmospheric conditions,radio noise, battery strength, and the like.

Range 814 is the LF polling range, which extends from the interior ofhost vehicle 812 and outwards up to around 2 through 4 meters. Asdiscussed above, the LF polling wakeup capability is provided as abackup to the disclosed UHF-based wakeup polling (e.g., which is usedwhen sufficient amounts of UHF noise inhibit the use of a UHF channelfor wakeup polling).

Range 816 is the LF RSSI range, which extends from the interior of hostvehicle 812 and outwards up to around 6 through 10 meters. As discussedabove, the range 816 can be reduced to an intermediate range of up toaround 4 through 6 meters to conserve power (e.g., when localization inthe range of 6 through 10 meters is not needed).

Range 818 is the UHF polling range, which extends from the interior ofhost vehicle 812 and outwards to around 10 meters or more. As discussedabove, using the UHF channel for wakeup polling saves a considerableamount of power over using an LF channel for wakeup polling. Providingthe LF channel-based polling wakeup capability as a backup to theUHF-based wakeup polling and using the LF channel for localizationallows for, for example, substantial decreases in power and maintainsaccuracy of localization over conventional solutions.

In an embodiment, a controller (e.g., such as a microcontroller or adigital signal processor) is used to control the signal strength and/orpolarization of signals 702, 704, 706, and 708. The variables aresoftware programmable, which allows more flexibility for implementingthe disclosed control schemes and provides an enhanced ability toadaptively adjust to dynamically changing conditions for optimizedsystem performance.

In various embodiments, the above described components can beimplemented in hardware or software, internally or externally, and sharefunctionality with other modules and components as illustrated herein.For example, the antenna 622 can be implemented outside of a deviceand/or upon a substrate (e.g., circuit board) upon which the passiveentry device 610 is located.

The combination of the long range UHF low power wake function and the LFlocalization functions can be used in various embodiments and used invarious identification or localization services. For example, theelectronic key can be embodied in a “smart-card-” and/or “identificationbadge-” device format and used to identify and localize users carryingsuch electronic keys. The determined identification and localizationinformation can be used to track and/or control movement of authorizedusers, even within a secured area. (The secured areas need not bedelimited by physical boundaries such as walls, fences, doors, and thelike.)

The various embodiments described above are provided by way ofillustration only and should not be construed to limit the claimsattached hereto. Those skilled in the art will readily recognize variousmodifications and changes that could be made without following theexample embodiments and applications illustrated and described herein,and without departing from the true spirit and scope of the followingclaims.

What is claimed is:
 1. A control unit comprising: an ultra-high frequency (UHF) transceiver; a low frequency (LF) transceiver; a memory storing instructions; and a processor coupled to the UHF transceiver, the LF transceiver, and the memory and configured to execute the instructions to cause the control unit to: transmit a plurality of UHF wakeup signals periodically using the UHF transceiver; receive a first transmission in response to one of the plurality of UHF wakeup signals, the first transmission containing an acknowledgement response; after receiving the first transmission, transmit a LF signal; receive a second transmission in response to the LF signal, the second transmission including a localization reply signal; determine a relative location of a source of the first and second transmissions based at least partially on the localization reply signal, transmit a plurality of LF wakeup signals using the LF transceiver, wherein at least one UHF wakeup signal is transmitted between the transmission of any two adjacent LF wakeup signals of the plurality of LF wakeup signals, and determine whether an amount of UHF noise exceeds a predetermined threshold, and wherein the plurality of LF wakeup signals are transmitted only if it is determined that the UHF noise exceeds the predetermined threshold.
 2. The control unit of claim 1, wherein: the acknowledgement response includes credential information of a source of the first transmission; and the execution of the instructions by the processor further cause the control unit to determine whether the source of the first transmission is valid based on the credential information.
 3. The control unit of claim 2, wherein the execution of the instructions by the processor further cause the control unit to execute at least one limited function in response to a determination that the credential information is valid, but not any non-limited function.
 4. The control unit of claim 3, wherein, after the relative location of the source is determined based on at least partially on the localization reply signal, the execution of the instructions by the processor further cause the control unit to execute at least one non-limited function.
 5. The control unit of claim 4, wherein: the control unit is a vehicle control unit of a vehicle; the source is a key fob paired to the vehicle control unit; and the non-limited function is starting an ignition of the vehicle.
 6. The control unit of claim 1, further comprising: a first antenna coupled to the UHF transceiver to transmit the plurality of UHF wakeup signals; and a set of second antennas coupled to the LF transceiver to transmit the LF signal, wherein each of the set of second antennas is arranged at a different position with respect to a reference point, and wherein the relative location of the source is determined using triangulation based on the localization reply signal and the position of each antenna of the set of second antennas.
 7. The control unit of claim 6, wherein using triangulation based on the localization reply signal and the position of each antenna of the set of second antennas includes using time of arrival information.
 8. The control unit of claim 1, wherein the localization reply signal includes received signal strength indicator (RSSI) information.
 9. The control unit of claim 1, wherein: a frequency range of the UHF transceiver is between 300 MHz and 2.4 GHz; and a frequency range of the LF transceiver is between 18 KHz and 150 KHz.
 10. The control unit of claim 1, wherein the execution of the instructions by the processor further cause the control unit to stop transmitting the plurality of UHF wakeup signals when the first transmission containing the acknowledgement response is received.
 11. An electronic key comprising: a first antenna; an ultra-high frequency (UHF) wake receiver coupled to the first antenna; a UHF transmitter; a second antenna; a low frequency (LF) receiver coupled to the second antenna; a memory storing instructions; and a processor coupled to the UHF transceiver, the LF receiver, and the memory and configured to execute the instructions to cause the electronic key to: receive, at the first antenna, a UHF wakeup signal; in response to receiving the UHF wakeup signal, power up the UHF transmitter and transmit an acknowledgement response; after transmitting the acknowledgement response, receive, at the second antenna, a LF signal; determine a received signal strength indicator (RSSI) measurement based on the received LF signal; and transmit the RSSI measurement as part of a localization reply signal; and a LF backup channel to receive LF wakeup signals concurrently with receiving the UHF wakeup signal.
 12. The electronic key of claim 11, wherein the second antenna is a three-dimensional antenna and the LF receiver includes a three-dimensional receiver.
 13. The electronic key of claim 11, wherein the acknowledgement response is transmitted as a UHF signal.
 14. The electronic key of claim 11, wherein the electronic key is configured as a key fob device for pairing with a vehicle control unit of a vehicle, and wherein the electronic key further comprises a three-dimensional immobilizer to allow starting an ignition of the vehicle. 